Ultrasonic Pumps

Electrohydrodynamic pumps, electroosmotic pumps, ultrasonic pumps and... 

Ultrasonic Pumps, Fig. 1 Schematic drawing of a typical SAW device used for driving droplets on a free surface... 

An ultrasonic transducer is an integrated component of acoustic pumps. The transducers that generate ultrasonic energy with megahertz frequency for ultrasonic pumps make use of the piezoelectric effect. A piezoelectric layer is the vital component of the ultrasonic transducer and provides the oscillatory motion that ultimately produces the surface acoustic waves (a good review on IDT and SAW can be found elsewhere [3]). 

Ultrasonic Pumps, Fig. 2 A1 pi droplet on aZnO SAW device before (a) and after (b) being driven by a RF frequency (Reprinted from Ref. [9] with the permission from Dr. Milne and Journal of Applied Physics)... 

Acoustic waves can potentially damage biological samples (e.g., cause cell lysis). Due to this reason, careful control of the SAW frequency and device optimization are necessary. Understanding the complicated mechanisms governing the fluid-structure interactions will help in the optimization of ultrasonic pumps dealing with biological samples. 

Rife JC, Bell MI, Horwitz JS, Kabler MN, Auyeung RCY, Kim WJ (2000) Miniature valveless ultrasonic pumps and mixers. Sens Actuator 868 135-140... 

Hasegawa T, Koyama D, Nakamura K, Ueha S (2008) A design of a miniature ultrasonic pump using a bending disk transducer. J Electroceiam 20 145-151... 

J. C. Rife, etal,. Miniature Valveless Ultrasonic Pumps and Mixers Sens., Actuators A, 2000, 86, 135-140. 

Ultrasonic pumps are pumps that use acoustic streaming to create a fluid motion inside microchannels. Acoustic streaming is the time-averaged flow induced hy an ultrasonic wave (periodic pressure oscillation). Attenuation of the acoustic energy (via reflection and other distortion) generates a body force within the fluid and converts acoustic energy into kinetic energy of the fluid [1]. 

Ultrasonic pumps are very useful for microscale applications due to their simphcity, robustness and scaling advantages. Moreover, they are insensitive to the chemical state of the fluid and the waU material unlike electroosmotic and magnetic pumps. By using acoustic streaming as a pumping mechanism, noncontact fluid control is achievable since no contact is needed between the acoustic source and the fluid and no valves are required [2]. 

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